The present invention relates to saws, and more particularly to a circle cutting device that readily attaches to a saw armor another easily accessible portion of a saw for guiding a workpiece into a moving saw blade thereby cutting accurate circles.
Circle cutting devices commonly used in such industries as for example wood-working, pattern making and furniture manufacture, typically attach to a sawing apparatus and direct a workpiece into a saw blade so as to precisely cut circles or partial arcs from the workpiece. More specifically, the devices of the prior art provide a stable pivot point for the workpiece to rotate about, enabling the blade to cut a well-proportioned circle. In addition, the circle cutting devices provide for repeatability and accuracy in cutting when cutting a series of several circles identical in size. The user adjusts the device to a position on the workpiece that corresponds to the radius of the diameter of the circle to be cut. The devices used in the aforementioned industries are typically adapted for band saws and table saws. For example, U.S. Pat. No. 3,995,521, issued to Raphael on Dec. 7, 1976, discloses an apparatus for cutting circles with band saws. This type of saw uses a blade consisting of a circle that is threaded through an upper housing and below a flat table or working surface. The blade is thus a continuous vertically oriented band that rotates through the upper housing and the work support table. Raphael teaches a cutting device including a base that extends outwardly from the band saw table. A vertically threaded bolt is threaded through a block which attaches to a support arm of the base. The block is moved along the support arm into the desired position and the bolt is rotated until the end of the bolt engages a workpiece placed on the saw table. Other circle cutting devices found in the prior art are appropriate for attachment to table saws. This type of saw uses a circular toothed blade having a diameter ranging from approximately six to seven inches. The blade is mounted below the table surface and vertically projects through a slot in the table. In one example, U.S. Pat. No. 5,231,905, issued to Trahan on Aug. 3, 1993, discloses an accessory that attaches to the table portion of a saw. The accessory has a planar frame with a protruding member that engages an existing slot in the saw table. A stationary pivot pin attached to an adjustable arm secures to the planar frame. The arm is moved until the pivot pin is in the desired position and then a set screw tightens the arm-pin assembly into place. The workpiece is then placed on the pin and secured to the table with clamps providing stable alignment for circle cutting. Still other devices known in the prior art for use with various cutting apparatus secure beneath the saw table, or to an extension extending from the table. For example, U.S. Pat. No. 4,693,155 issued to Ledford on Sep. 15, 1987, discloses a saw attachment that secures beneath the saw table. A frame with a movable carriage having a centering pin is mounted directly beneath the work table of the saw. An actuating device moves the carriage into position along a threaded rod parallel to the workpiece. The position of the carriage corresponds to the desired diameter of the circle to be cut. The diameter is defined by an adjusting stop located on the threaded rod. Although the devices of the prior art serve the intended purpose of providing a pivot point for guiding a workpiece into a saw blade so as to accurately cut a circle or the like, their use is limited to band saws, table saws, or other cutting apparatus having accessible table space for affixing the device either below the table or directly on to the upper surface of the table. Furthermore, most of the cutting devices known in the prior art include pivot pins and other combination of parts which result in a complex assembly requiring excess set up time to properly align on a workpiece before sawing to insure accurate cutting.
There exists a need for a circle cutting device that is easily adjustable with minimum set up time and readily accessible during the cutting process. In addition, there exists a need for a circle cutting device that can be used with a jigsaw and more particularly suited for a jigsaw as disclosed in U.S. Pat. No. Des. 325,588 issued to A. S. Bohrer on Apr. 21, 1992, and Des. No. 328,751 issued to S. P. Bohrer on Aug. 18, 1992. These saws are characterized by a horizontal arm extending across the table portion of the saw. As contrasted with band saws and table saws, jigsaws typically use a relatively short, narrow blade approximately 6 to 10 inches in length. The saws illustrated in the two Bohrer patents are well known in the steel rule die industry as retractable jigsaws that are characterized by having vertically reciprocating saw blades wherein the blade is generally connected only at one point above the table top and not connected below the table top. Thus, the saw blade can retract above the table top when the saw is not operating.